JP2018059091A - Method for producing prepreg - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing prepreg capable of obtaining prepreg which can suppress formation of pinholes of a surface of a molded product.SOLUTION: A method for producing a prepreg formed by impregnating a reinforced-fiber with a matrix resin includes a decompression heating step of decompressing a laminate 1 in which a prepreg 18 formed by impregnating a reinforced-fiber base material with a matrix resin composition is sandwiched between a first sheet 10 and a second sheet 16 with a relative pressure of -101.0 to -98.0kPa while heating the laminate at 65-85°C.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for producing a prepreg.

  A molded article made of a fiber reinforced composite material formed of a reinforced fiber and a matrix resin composition is lightweight and has excellent mechanical properties, and thus is widely used in various applications such as aircraft and vehicles. In the production of such molded articles, sheet-like prepregs, which are intermediate substrates, in which a reinforcing fiber substrate is impregnated with a matrix resin composition are widely used. After a plurality of prepregs are laminated, a molded product is obtained by heating and pressing to mold. In particular, when a cross prepreg having reinforced fibers as a woven fabric is used for the outermost layer of the molded product, a fiber reinforced composite material having excellent design properties can be obtained.

Examples of the method for producing the prepreg include the following methods.
A resin film formed by applying a matrix resin to a release paper or the like is laminated on at least one surface of a reinforcing fiber base material such as a cloth material woven with reinforcing fibers, and is pressed with a pressure roll while heating the matrix. A prepreg is obtained by impregnating the reinforcing fiber base with the resin composition.

In autoclave molding using the obtained prepreg, a plurality of prepregs are generally laminated in a mold.
However, when the prepreg obtained by the above method is used, pinholes may be formed on the mold surface side of the prepreg in the molded product. When pinholes are formed on the surface of the molded product, the design properties are degraded. Further, when coating is performed after molding, the diameter of the pinhole is enlarged, and the problem of deterioration in design properties becomes more prominent.

When a pinhole is generated on the surface of the molded product, the pinhole is also filled with a masking material containing a filler or the like. However, in this method, since it is necessary to individually fill each pinhole formed in the prepreg, the work is complicated and time consuming, and the cost increases.
In order to suppress such appearance degradation due to pinholes, Patent Document 1 discloses a cross prepreg made of a matrix resin containing carbon black.

JP 2014-162858 A

However, carbon black has the effect of making the generated pinholes inconspicuous, but in reality, the generation of pinholes cannot be suppressed.
An object of this invention is to provide the manufacturing method of the prepreg from which the prepreg which can suppress the pinhole formation of the surface of a molded article is obtained, without using a special additive.

The present invention has the following configuration.
[1] heating the prepreg impregnated with the matrix resin composition into the reinforcing fiber base material laminate sandwiched between the first sheet and the second sheet, while reducing the pressure at 10 to 35 ° C. lower temperature from below the temperature T _A The manufacturing method of a prepreg which has a pressure reduction heating process to do.
Temperature T _A : Temperature showing the lowest viscosity (Pa · s) in the temperature rising viscosity measurement in which the viscosity is continuously measured while the matrix resin composition is heated from 25 ° C. to 200 ° C. at a temperature rising rate of 2 ° C./min. .
[2] A reduced pressure heating step of heating a laminated body in which a prepreg impregnated with a matrix resin composition into a reinforcing fiber substrate is sandwiched between a first sheet and a second sheet at 65 to 85 ° C. while reducing the pressure, A method for producing a prepreg.
[3] enhance the fiber base prepreg obtained by impregnating a matrix resin composition laminated body sandwiched between the first sheet and the second sheet, the viscosity following viscosity below the temperature T _A, and the matrix resin composition having a vacuum heating step of heating while reducing the pressure at the temperature indicated below mu _a greater than _{Pa · s μ a + 65Pa ·} s, the production method of the prepreg.
Temperature T _A : Temperature showing the lowest viscosity (Pa · s) in the temperature rising viscosity measurement in which the viscosity is continuously measured while the matrix resin composition is heated from 25 ° C. to 200 ° C. at a temperature rising rate of 2 ° C./min. .
Viscosity μ _A : Minimum viscosity (Pa · s) in the temperature rising viscosity measurement in which the viscosity is continuously measured while the matrix resin composition is heated from 25 ° C. to 200 ° C. at a temperature rising rate of 2 ° C./min.
[4] The viscosity of the matrix resin composition said to be continuously measured during the Atsushi Nobori viscosity measurement is _in the range of 0.5~65Pa · s in a temperature range of T A -35 ° C. until _T A -10 ° C. The method for producing a prepreg according to [1].
[5] The method for producing a prepreg according to any one of [1] to [4], wherein the laminate is decompressed by vacuum bagging.
[6] The method for producing a prepreg according to any one of [1] to [5], wherein the reinforcing fiber base material is a cloth material.
[7] The method for producing a prepreg according to any one of [1] to [6], wherein a relative pressure in the reduced pressure heating step is −101.0 to −98.0 kPa.

  According to the method for producing a prepreg of the present invention, a prepreg capable of suppressing the formation of pinholes on the surface of a molded product can be obtained without using a special additive.

It is sectional drawing which shows the impregnation process of the manufacturing method of the prepreg of this invention. It is sectional drawing which showed an example of the vacuum heating process in the manufacturing method of the prepreg of this invention. It is sectional drawing which showed an example of the vacuum heating process in the manufacturing method of the prepreg of this invention. It is the perspective view which showed an example of the vacuum heating process in the manufacturing method of the prepreg of this invention. 3 is a graph showing the results of temperature-rising viscosity measurement of a matrix resin composition in Experimental Example 1.

The method for producing a prepreg of the present invention is a reduced pressure in which a laminated body in which a prepreg impregnated with a matrix resin composition in a reinforcing fiber substrate is sandwiched between a first sheet and a second sheet is heated at a specific temperature while reducing the pressure. It is a method having a heating step. By performing the reduced pressure heating step, a prepreg capable of suppressing the formation of pinholes on the surface of the molded product is obtained.
Hereinafter, an example of the manufacturing method of the prepreg of the present invention will be described and described.

The manufacturing method of the prepreg of this embodiment has the following impregnation process and pressure reduction heating process.
Impregnation step: The matrix resin composition film (resin film) coated on the first and / or second sheet is laminated on the reinforcing fiber base and then heated and pressed to strengthen the matrix resin composition. A fiber base material is impregnated to form a laminate.
Reduced pressure heating step: A laminate in which a prepreg impregnated with a matrix resin composition in a reinforcing fiber substrate is sandwiched between a first sheet and a second sheet is heated at a specific temperature while reducing the pressure.

(Impregnation process)
For example, as shown in FIG. 1 (A), a matrix resin composition is continuously applied onto the first sheet 10 while the strip-shaped long first sheet 10 is conveyed in one direction, A film 12 is formed. It does not specifically limit as the 1st sheet | seat 10, The well-known release paper and film normally used for manufacture of a prepreg can be used. Examples of the film include a resin film such as polyethylene terephthalate which is excellent in heat resistance and stretching characteristics. Release paper is preferred because it does not stretch during heating during impregnation and does not stick to a roll.
The method for coating the matrix resin composition is not particularly limited, and a known coating method can be employed.

  The matrix resin composition may be a thermosetting resin or a thermoplastic resin, but is preferably a thermosetting resin that has excellent resin impregnation properties and easily exhibits mechanical properties. As a thermosetting resin, the well-known thermosetting resin used for a prepreg can be used, For example, an epoxy resin, a phenol resin, an unsaturated polyester resin, a urethane type resin, a urea resin, etc. are mentioned. Especially, as a thermosetting resin, an epoxy resin is preferable from a viewpoint of the mechanical physical property of a molded article. As a thermosetting resin, 1 type may be used independently and 2 or more types may be used together.

  For matrix resin compositions, flame retardants, weather resistance improvers, antioxidants, heat stabilizers, UV absorbers, plasticizers, lubricants, colorants, compatibilizers, non-fibrous fillers, conductive materials You may mix | blend additives, such as a property filler, a mold release agent, and surfactant. As an additive, 1 type may be used independently and 2 or more types may be used together.

Next, as shown in FIG. 1B, the reinforcing fiber base material 14 is disposed on the resin film 12.
As the form of the reinforcing fiber base, for example, a UD sheet (unidirectional sheet) in which a large number of long reinforcing fibers are aligned in one direction, a cloth material made by weaving reinforcing fibers into a woven fabric, and a nonwoven fabric made of reinforcing fibers Etc. Among these, a cloth material is preferable from the viewpoint of the design properties of the molded product. The cloth material is a cloth material of any woven structure such as a unidirectional woven fabric in which reinforcing fibers are arranged in a required direction, a bi-directional woven fabric such as plain weave, satin weave, twill weave, triaxial woven fabric, non-crimp woven fabric, etc. However, it is particularly preferable to use plain weave excellent in design and twill weave excellent in design and workability. As a reinforced fiber base material, 1 type may be used independently and 2 or more types may be used together.

  Examples of the reinforcing fiber constituting the reinforcing fiber base include carbon fiber, aramid fiber, silicon carbide fiber, alumina fiber, boron fiber, tungsten carbide fiber, and glass fiber. Among these, carbon fibers are preferable as the reinforcing fibers because they are excellent in specific strength and specific elastic modulus. As reinforcing fiber, 1 type may be used independently and 2 or more types may be used together.

Basis weight of the reinforcing fiber base material is preferably from ^{70~800g / m 2, 150~250g / m} 2 is more preferable. If the basis weight of the reinforcing fiber base is within the above range, the impregnation property of the matrix resin composition is good. If it is 70 g / m ² or more, a molded article having a better appearance can be obtained. If it is 150 g / m ² or more, a molded article having a smooth surface can be obtained at low cost. If it is 800 g / m ² or less, the processing of the reinforcing fiber substrate becomes easy.

  Furthermore, the matrix resin composition is applied onto the second sheet 16 to form the resin film 12, and the second sheet 16 and the resin film are formed on the reinforcing fiber base 14 as shown in FIG. 12 are laminated to obtain a precursor laminate 1A of the first sheet 10, the resin film 12, the reinforcing fiber substrate 14, the resin film 12, and the second sheet 16. As the 2nd sheet | seat 16, the well-known release paper and film normally used for manufacture of a prepreg can be used. Examples of the film include a resin film such as polyethylene terephthalate which is excellent in heat resistance and stretching characteristics.

  Next, the precursor laminate 1 </ b> A is pressed in the thickness direction by passing a pressing roll or the like, and the reinforcing fiber substrate 14 is impregnated with the matrix resin composition forming the resin film 12. As a result, as shown in FIG. 1D, the laminate 1 in which the prepreg 18 is sandwiched between the first sheet 10 and the second sheet 16 is obtained.

Prior to the subsequent reduced pressure heating step, the first sheet and the second sheet used for the production of the prepreg may be replaced with another sheet (not shown) as necessary. As the other sheet, a known release paper or film usually used for prepreg production can be used. Examples of the film include a polyolefin film such as a polyethylene film.
When the first and / or second sheets are replaced before the reduced pressure heating step, the sheets attached to both surfaces of the prepreg are handled as the first and second sheets, respectively, in the subsequent steps. .

(Reduced pressure heating process)
For example, the laminated body 1 is cut into a size corresponding to a molded product, and the temperature rise rate is 1 to 10 ° C. while the relative pressure is reduced to −101.0 to −98.0 kPa with respect to the laminated body 1 after cutting. Heat to 65-85 ° C./min and hold for 5-30 minutes. Thereby, the prepreg which can suppress formation of the pinhole on the surface of a molded article is obtained.

Decompression of the laminate 1 is preferably performed by vacuum bagging. Specifically, for example, as shown in FIG. 2, the laminated body 1 is covered with a vacuum bag 50 (bag film), sealed with a sealing tape and bagged, and then the internal air is extracted through a pressure reducing valve 52. Depressurize and vacuum bagging. The laminate 1 may be used by laminating two or more.
In this state, the laminated body 1 can be heated by heating the vacuum bag 50 containing the laminated body 1 with heating equipment such as a heating furnace.

  The method for depressurizing the laminate is not limited to the form illustrated in FIG. For example, a method of performing vacuum bagging using the vacuum bagging apparatus 100 illustrated in FIGS. 3 and 4 may be used. The vacuum bagging apparatus 100 includes a pair of rectangular first frame body 102 and second frame body 104. A flexible and stretchable rubber sheet 106 is attached to the second frame 104 side of the first frame 102 so as to cover the opening, and the first frame 102 and the rubber sheet 106 are attached. Are bonded and integrated. A flexible and stretchable rubber sheet 108 is attached to the second frame body 104 on the first frame body 102 side so as to cover the opening, and the second frame body 104 and the rubber sheet 108 are attached. Are bonded and integrated.

  In the vacuum bagging apparatus 100, the first frame body 102 and the second frame body 104 are brought close to each other and the laminated body 1 is sandwiched between the pair of rubber sheets 106 and 108. , 108 is extracted and decompressed to enable vacuum bagging. The laminated body 1 can be heated by heating the vacuum bagging apparatus 100 in this state with heating equipment such as a heating furnace.

  Further, in the present invention, in addition to vacuum bagging, the pressure may be reduced by extracting and reducing the pressure in the box in a state where the laminated body is installed in the box.

The heating temperature is 10 to 35 ° C. lower than the temperature T _A (° C.). That is, if the heating temperature in the reduced pressure heating step is T (° C.), T _A −35 ≦ T ≦ T _A −10. The heating temperature T is preferably T _A −30 ≦ T ≦ T _A −10 and more preferably T _A −25 ≦ T ≦ T _A −10.
Temperature T _A : _A temperature showing the lowest viscosity (Pa · s) in the temperature rising viscosity measurement in which the viscosity is continuously measured while heating the matrix resin composition from 25 ° C. to 200 ° C. at a temperature rising rate of 2 ° C./min.
If it is more than the said lower limit, processing time will not become long too much and productivity will become favorable. If the heating temperature is equal to or lower than the above upper limit value, excessive progress of the prepreg gelation reaction can be suppressed, resulting in defects such as bending failure in the post-process and poor bonding between the prepregs. This can be suppressed. When the heating temperature is within the range of T _A −25 ≦ T ≦ T _A −10, a molded product with particularly good appearance quality can be obtained in a short time.

The upper limit of the heating temperature, the less than T _A, and the temperature is preferably showing a larger value following viscosity μ _A Pa · s viscosity of the matrix resin composition, more preferably the temperature is showing a μ _{A +} 1Pa · s , Μ _A +2 Pa · s is more preferable.
The lower limit of the heating temperature, the less than _{T A,} and the temperature is preferably exhibits the following viscosity _{μ A} + 65Pa · s viscosity of the matrix resin composition, more preferably the temperature is showing a _{μ A + 50Pa · s, μ} A + 30Pa · _A temperature indicating s is more preferable, and a temperature indicating μ _A +20 Pa · s is particularly preferable.
Viscosity μ _A : The lowest viscosity (Pa · s) in temperature rising viscosity measurement in which the viscosity is continuously measured while heating the matrix resin composition from 25 ° C. to 200 ° C. at a temperature rising rate of 2 ° C./min.
If it is in the said range, since the fluidity | liquidity of a matrix resin composition is good, a molded article with a favorable external appearance quality is obtained in a short time.

  In the case of a thermosetting resin that cures at 130 ° C, the heating temperature is preferably 65 to 85 ° C, more preferably 70 to 85 ° C, and even more preferably 75 to 85 ° C. If heating temperature is 65 degreeC or more, processing time will not become long too much and productivity will become favorable. If the heating temperature is 85 ° C. or lower, it is possible to suppress excessive progress of the prepreg gelation reaction, resulting in problems such as a bending failure in the post-process and a poor adhesion between the prepregs or between the prepregs. Can be suppressed. When the heating temperature is 75 ° C. or higher and 85 ° C. or lower, a molded product having a particularly good appearance quality can be obtained in a short time.

T viscosity of the matrix resin composition is continuously measured during the Atsushi Nobori viscosity _{measurements, 0.5~65Pa} · _s in a temperature range of T A -35 ° C. until _T A -10 ° _C., the T A -30 ° C. 0.5~50Pa · _s in the temperature range of up to _a -10 ° _C., preferably in the range of 0.5~20Pa · s in a temperature range of T a -25 ° C. until _T a -10 ° C..
Within the above range, the curing reaction of the matrix resin composition does not start, and the matrix resin composition exhibits an appropriate fluidity, so that a molded article having a particularly good appearance quality can be obtained in a short time.

The viscosity of the matrix resin composition is continuously measured during the Atsushi Nobori viscosity measurement is preferably the difference between the viscosity mu _A is equal to or less than the greater than 50Pa · s 0Pa · s in the temperature range of 65 to 85 ° C., 70 more preferably the difference is less than greater 30 Pa · s than 0 Pa · s and a viscosity mu _a at a temperature in the range of to 85 ° C., the difference between the viscosity mu _a in the temperature range of 75-85 ° C. is greater than 0 Pa · s More preferably, it is 15 Pa · s or less.
The viscosity of the matrix resin composition is continuously measured during the Atsushi Nobori viscosity _{measurements,} T A -35 large difference between the viscosity mu _A is from 0 Pa · s at a temperature ranging from ° C. to _T A -10 ℃ 65Pa · s preferably _less, more preferably the difference between the viscosity mu _a is not more than 0 Pa · s greater than 30 Pa · s in a temperature range of T a -30 ° C. until _T a -10 _{℃, T} a -25 the difference between the viscosity mu _a in the temperature range up to _T a -10 ° C. from ° C. is further preferably less large 15 Pa · s than 0 Pa · s.
Since the viscosity of the matrix resin composition is within the above-mentioned temperature range and the viscosity range does not start, the matrix resin composition does not start and the matrix resin composition exhibits appropriate fluidity. The easiest to obtain.

  What is necessary is just to set a heating time suitably according to heating temperature, 5 to 30 minutes are preferable and 10 to 20 minutes are more preferable. If the heating time is equal to or greater than the lower limit value, a stable quality prepreg can be obtained, and if the heating time is equal to or less than the upper limit value, the productivity is improved.

  Heating and pressure reduction in the reduced pressure heating step may be started simultaneously, or one of them may be started first. From the viewpoint that the operation is simple, a method of starting heating in a state where the laminated body is depressurized is preferable.

The heating rate is preferably 1 ° C./min to 10 ° C./min. If it is 1 degreeC / min or more, a molded article can be obtained with favorable productivity. If it is 10 degrees C / min or less, since the capability of a heater does not become excessive, capital investment does not become excessive and power consumption does not increase too much, so that it is excellent in economic efficiency.
In the reduced pressure heating process, the laminated body 1 vacuum bagged as required is put into a heating furnace, and even if the temperature rise is started from room temperature, the laminated body 1 vacuum bagged is set to the heating holding temperature as necessary. May be put into a heated furnace.

  The decompression is preferably performed so that the relative pressure is −101.0 to −98.0 kPa. If it is −98.0 kPa or less, a molded article having a good appearance can be obtained.

The number of the stacked bodies 1 in the vacuum bagging illustrated in FIGS. 2 and 3 is one, but the decompression process may be performed in a state where two or more are stacked. As the number of stacked bodies stacked in the vacuum bagging increases, the effect of suppressing the formation of pinholes in the molded product due to the prepreg of the stacked body disposed in the central portion in the thickness direction becomes smaller. Therefore, the number of stacked bodies when a plurality of stacked bodies are stacked and vacuum bagging is performed depends on the area of the stacked body, but is preferably 2 to 8, and particularly preferably 2 to 4.
If the number is two or more, the productivity is good, and if the number is eight or less, the heat transfer is good, so that a prepreg having a stable quality can be obtained.

The prepreg obtained by the production method of the present invention can be used for the production of a molded product. As a method for producing a molded product, a known method can be employed, and examples thereof include autoclave molding, vacuum bag molding, and press molding. The method for producing a prepreg of the present invention is particularly useful when a molded product is produced by autoclave molding.
In the autoclave molding, for example, the laminated body 1 taken out from the vacuum bag 50 after the reduced pressure heating process is cut according to the shape of the molded product. Next, the prepreg 18 from which the first sheet 10 and the second sheet 16 are removed from the laminate 1 is attached to a mold. Further, a predetermined number of prepregs 18 are laminated, bagged with a resin film or the like, depressurized, put into an autoclave, and heated and pressurized to obtain a molded product.

As described above, the method for producing a prepreg of the present invention includes a reduced-pressure heating step in which the prepreg is depressurized while heating the laminated body sandwiched between the first sheet and the second sheet at a specific temperature. By performing the reduced pressure heating step, a prepreg capable of suppressing the formation of pinholes on the surface of the molded product is obtained.
When a cloth material is used for the reinforcing fiber base, the matrix resin composition is less likely to be impregnated than the UD sheet, and voids and pinholes are likely to occur in the prepreg, so that pinholes tend to be formed on the surface of the molded product. There is. However, in the production method of the present invention, a prepreg capable of suppressing the formation of pinholes on the surface of a molded product can be obtained even when a cloth material is used for the reinforcing fiber substrate.

Although it is not necessarily clear as a factor by which the pinhole formation on the surface of a molded article is suppressed by using the prepreg obtained by performing a pressure reduction heating process, the following things can be considered.
In the prepreg obtained by impregnating the reinforcing fiber base material with the matrix resin composition, the matrix resin composition flows in the reduced pressure heating step, and pinholes and voids on the prepreg surface are reduced. This is considered to be one of the factors that suppress the generation of pinholes on the surface of a molded product produced using the prepreg.
Further, it is considered that the shape of the prepreg changes due to softening of the matrix resin composition in the reduced pressure heating step, and the dent on the prepreg surface, particularly the crimp portion, becomes shallow. As a result, the air trapped in the dent of the surface in contact with the mold in the prepreg is likely to be sucked and removed by the reduced pressure during molding, which is considered to be a factor that suppresses the formation of pinholes on the surface of the molded product. .

  In addition, the manufacturing method of the prepreg of this invention is not limited to an above described method. For example, in the impregnation step, the matrix resin composition may be impregnated from one side of the reinforcing fiber base.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by the following description.
[Measurement of temperature rise viscosity of matrix resin composition]
The temperature rising viscosity of the matrix resin composition was measured as follows. The viscosity at 30 ° C. of the obtained measurement result was defined as “viscosity at 30 ° C.” of the matrix resin composition. Furthermore, in the obtained measurement result, the temperature showing the lowest viscosity in the temperature range from 25 ° C. to 200 ° C. was defined as “temperature T _A ”.
Device: AR-G2 (manufactured by TA Instruments)
Use plate: 35mmΦ parallel plate Plate gap: 0.5mm
Measurement frequency: 10 rad / sec Temperature rising rate: 2 ° C./min Stress: 3000 dynes / cm ²

[Form appearance evaluation]
The mold side surface of the molded product obtained in each example and comparative example was visually evaluated.
(Evaluation criteria)
The molded appearance evaluation before coating was performed according to the following criteria.
A: There are almost no pinholes.
○: There are few pinholes.
X: There are many pinholes.

[Materials used]
TR3523: Cross prepreg manufactured by Mitsubishi Rayon Co., Ltd. Trade name: TR3523 320GMP.
TR3110: Cross prepreg manufactured by Mitsubishi Rayon Co., Ltd. Trade name: TR3110 320GMP.
TRK510: Cross prepreg manufactured by Mitsubishi Rayon Co., Ltd. Trade name: TRK510 321GMP.

[Example 1]
Two sheets of prepreg (trade name: TR3523 320GMP, manufactured by Mitsubishi Rayon Co., Ltd.) impregnated with an epoxy resin composition in a cloth material are laminated without peeling, and a breather cloth (OS Corporation) After the product, product name: OSE-135) was placed, it was covered with a polypropylene bag (manufactured by Toray Film Processing Co., Ltd., product name: RAYFAN NO, product number 50 TYPE1600RT 1524 mm). Next, the polypropylene bag was sealed with a sealing tape (trade name: VG635, manufactured by Nippon Sika Co., Ltd.) and bagged. The polypropylene bag sealed with the above-mentioned sealing tape was placed in an autoclave (Iwata Seisakusho, Autoclave ACA) in a state where the pressure was reduced by a vacuum pump (Osaka Air Machinery Co., Ltd., oil rotary KV-2S), and heated. During the autoclave treatment, the pressure reduction was continued within a range of -101.0 to 98.0 kPa with a vacuum pump (Osaka Air Machinery Co., Ltd., oil rotary KV-3S). The degree of reduced pressure was measured with a vacuum degree measuring device (manufactured by Keyence Corporation, digital pressure sensor AP-31A). The heating in the reduced pressure heating step was performed by raising the temperature from 25 ° C. to 70 ° C. at 3.3 ° C./min, holding at 70 ° C. for 30 minutes, and lowering the temperature at 2 ° C./min.
Next, the obtained prepreg was cut into a size of 300 mm × 300 mm, and then the release paper and the polyethylene film were peeled off, and then one sheet was laminated on a mold. Further, the prepreg (Mitsubishi Rayon was cut into a size of 300 mm × 300 mm). After peeling off the release paper and the polyethylene film (trade name: TRK510 321GMP) manufactured by Co., Ltd., one sheet was laminated, then bagged with the same polypropylene film, depressurized, placed in an autoclave, heated and pressurized to form I got a product. After heating from 25 ° C. to 80 ° C. at 1.4 ° C./minute, hold at 80 ° C. for 30 minutes, then increase to 1.4 ° C./minute to 130 ° C. and hold for 70 minutes. The temperature was lowered at 2.0 ° C./min. The pressurization was started at the start of the temperature rise, and after increasing the pressure at 20 kPa / min, the pressure was maintained at 600 kPa for 185 minutes, and then the pressure was reduced at a pressure reduction rate of −100 kPa for 3 minutes to return to the atmospheric pressure.
The molded product thus obtained was evaluated for molding appearance. The results are shown in Table 1.

[Examples 2 to 4, Comparative Example 4]
Except that the conditions of the prepreg reduced pressure heating step were changed as shown in Table 1, the prepreg was subjected to reduced pressure heating treatment in the same manner as in Example 1, and was laminated in the same manner as in Example 1 to obtain a molded product. The molded product thus obtained was evaluated for molding appearance in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
A prepreg was laminated to obtain a molded product in the same manner as in Example 1, except that the prepreg was not subjected to the reduced pressure heating step. The molded product thus obtained was evaluated for molding appearance in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
The prepreg was heat-treated in the same manner as in Example 1 except that bagging was not performed and the decompression process was not performed, and a molded product was obtained by laminating in the same manner as in Example 1. The molded product thus obtained was evaluated for molding appearance in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 3]
A cross prepreg manufactured by Mitsubishi Rayon Co., Ltd. (trade name: TR3110 320GMP) is used in place of the cross prepreg manufactured by Mitsubishi Rayon Co., Ltd. (trade name: TR3110 320GMP). The prepreg was heat-treated in the same manner as in Example 1 except that it was pressurized using a press (manufactured by Takagi Metal Industry Co., Ltd., model XS-E) and heated at 85 ° C. for 10 minutes. As a result, a molded product was obtained. The molded product thus obtained was evaluated for molding appearance in the same manner as in Example 1. The results are shown in Table 1.

  In addition, “VH” in Table 1 means a method of performing a reduced pressure heating process.

  As shown in Table 1, in Examples 1 to 4 using the prepreg obtained by performing the reduced pressure heating process, compared to Comparative Examples 1 to 3 using the prepreg not performing the reduced pressure heating process, Pinholes were suppressed. Moreover, in the comparative example 4, since the temperature of the pressure reduction heating process was low, the molded appearance was not good.

[Experimental Example 1]
Temperature rising viscosity measurement for continuously measuring the viscosity of the epoxy resin composition, which is a matrix resin composition of TR3523 320GMP used in Example 1, from 25 ° C. to 130 ° C. at a heating rate of 2 ° C./min. Went. The result is shown in FIG.
Viscosity mu _A is 2.3Pa · s, the temperature _{T A} is 98.4 ° C., a temperature _T A -35 viscosity ° C. is 62.8Pa · s, the temperature _T A -10 viscosity ° C. is 3.5 Pa · s, 65 The viscosity at 5 ° C. was 50.1 Pa · s, and the viscosity at 85 ° C. was 5.2 Pa · s.

DESCRIPTION OF SYMBOLS 1 Laminated body 1A Precursor laminated body 10 1st sheet | seat 12 Resin film | membrane 14 Reinforcement fiber base material 16 2nd sheet | seat 18 Prepreg 50 Vacuum bag 52 Pressure reducing valve 100 Vacuum bagging apparatus 102 1st frame body 104 2nd frame body 106 Rubber sheet 108 Rubber sheet 110 Pressure reducing valve

Claims (7)

Heating under reduced pressure to a prepreg obtained by impregnating a matrix resin composition into the reinforcing fiber base material laminate sandwiched between the first sheet and the second sheet is heated while reducing the pressure at 10 to 35 ° C. lower temperature from below the temperature T _A The manufacturing method of a prepreg which has a process.
Temperature T _A : Temperature showing the lowest viscosity (Pa · s) in the temperature rising viscosity measurement in which the viscosity is continuously measured while the matrix resin composition is heated from 25 ° C. to 200 ° C. at a temperature rising rate of 2 ° C./min. .   Manufacture of a prepreg having a reduced pressure heating step of heating a laminated body in which a prepreg impregnated with a matrix resin composition into a reinforcing fiber substrate is sandwiched between a first sheet and a second sheet at 65 to 85 ° C. while reducing the pressure. Method. Strengthen the fiber base prepreg obtained by impregnating a matrix resin composition laminated body sandwiched between the first sheet and the second sheet, the temperature T is less than _A, and the viscosity is below the viscosity mu _A Pa of the matrix resin composition -The manufacturing method of a prepreg which has a pressure reduction heating process heated while depressurizing at the temperature which shows more than (micro | micron | _A) + 65Pa * s more than s.
Temperature T _A : Temperature showing the lowest viscosity (Pa · s) in the temperature rising viscosity measurement in which the viscosity is continuously measured while the matrix resin composition is heated from 25 ° C. to 200 ° C. at a temperature rising rate of 2 ° C./min. .
Viscosity μ _A : Minimum viscosity (Pa · s) in the temperature rising viscosity measurement in which the viscosity is continuously measured while the matrix resin composition is heated from 25 ° C. to 200 ° C. at a temperature rising rate of 2 ° C./min. The viscosity of the matrix resin composition is continuously measured in the Atsushi Nobori viscosity measurement _is in the range of 0.5~65Pa · s in a temperature range of T A -35 ° C. until _T A -10 ° C., The method for producing a prepreg according to claim 1.   The manufacturing method of the prepreg as described in any one of Claims 1-4 which pressure-reduces by vacuum bagging the said laminated body.   The manufacturing method of the prepreg as described in any one of Claims 1-5 whose said reinforcement fiber base material is a cloth material.   The manufacturing method of the prepreg as described in any one of Claims 1-6 whose relative pressure of the said pressure reduction heating process is -101.0--98.0kPa.

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